1. Field of the Invention
The present invention relates to connectors for electrically connecting a coaxial cable to a threaded port.
2. Prior Art
The design and construction of F-type coaxial cable connectors, such as those commonly used for transmitting cable TV signals, digital data lines and home satellite systems, has changed in recent years in order to comply with changing industry standards and FCC regulations. Currently, connectors must exhibit a low RF leakage level, even in exposed environments. A moisture-proof seal between the connector and the conductor(s) within a coaxial cable is essential to prevent corrosion and RF leakage.
Connectors adapted to form a secure, electrically conductive connection between a coaxial cable and a threaded female port have been developed. Such prior art connectors are discussed, for example, in U.S. Pat. Nos. 5,024,605 to Ming-Hua, 4,280,749 to Hemmer, 4,593,964 to Forney, Jr. et al., 5,007,861 to Stirling, 5,073,129 to Szegda and 5,651,699 to Holliday. U.S. Pat. No. 5,879,191 to Burris, discusses prior art efforts to provide a coaxial connector which is moisture-proof and minimizes radiative loss of signal from the cable. A radial compression type of coaxial cable connector of the type generally used today, is described in detail in U.S. Pat. No. 5,632,651 to Szegda, and the disclosure of Szegda '651 relating to radial compression coaxial cable connectors is incorporated herein by reference thereto.
While the innovative plethora of prior art connectors, some of which are disclosed above, provide improved moisture sealing and/or RF leakage characteristics, all have inherent limitations. For example, the integrity of the attachment between the cable and connector is "craft sensitive", depending on the skill of the installer. The steps required in order to provide a secure, sealing engagement between a connector and a coaxial cable include opportunities for installation errors to occur. Installation of a coaxial cable connector on a coaxial cable requires that the end of the cable first be prepared to receive the connector. The connector is then manually forced onto the prepared end of the cable until the protective jacket and underlying conductive braid of the cable are separated from the dielectric core of the cable. The cable is further advanced into the connector by hand, which requires the application of substantial force by the installer, until the correct depth of insertion is attained. Finally, the connector is securely affixed to the cable by compressing the connector, again by hand, with a compression tool. With most prior art connectors, during the compression step, the cable jacket and conductive braid are compressed against an annular barb disposed on the surface of an underlying tubular shank during the final several millimeters of compressive travel. If the installer fails to completely compress the connector, especially in the final 20 percent of the compressive range, the connector may come loose. Incorrect installation will result in unacceptable levels of RF leakage.
Prior art connectors rely on a single point of compression (i.e., between the annular barb on the tubular shank and the body portion of the connector) for secure attachment to a coaxial cable. Accordingly, the barb on the tubular shank has a relatively high profile or angular pitch, which high profile makes it difficult to force the prepared end of a coaxial cable into the connector. A connector having a single point of compression requires the cable to have a jacket thickness lying within a small range of tolerances. Recent developments in building codes require that coaxial cable installed in particular locations within a structure, such as plenum areas, air return ducts and elevator shafts, have fire retardent jacketing materials. Such new jacketing materials have different physical properties than the standard coaxial cables previously used, such as elasticity, smoothness and thickness, which renders prior art connectors less than optimal for use therewith. The skilled artisan will appreciate that it would be an advancement in the art to provide a cable connector wherein the annular barb on the tubular shank has a relatively low profile, enabling the connector to accommodate the facile insertion of coaxial cable having a variety of thicknesses, elasticity and/or smoothness, and be securely attached to the cable. Accordingly, there remains a need for a cable connector that is impermeable to moisture, can be used with a variety of cable jacket and braid thicknesses and is easy to install with minimum chance for error.